Overview

Driver PCB for up to 64 common-anode RGB LEDs, or 192 normal LEDs.
The PCB is designed for 1:3 multiplexing of the LEDs, and is equipped with 8 74HC595 shift registers (configured as 4 16-bit deep registers), 64 current-limiting resistors (220 Ohm by default) and 3 FETs to switch the cathode groups on-and-off.
The PCB is equipped with a BitWizard-standard 20-pin IO connector, designed to work together with our USB-multio PCB, but it is also possible to connect our FTDI-ATmega, USB-bigmultio or Cyclone dev board, or one of your own boards, like for example an Arduino.

SV1-SV8 are the connectors for the RGB LEDs. SV1-SV8 are connected to IC1-IC8.
IC1 and IC5 are configured as one 16-bit deep shift register. Qa-Qh are connected to IC1, and Qi-Qp are connected to IC5.
IC2 and IC6 are configured as one 16-bit deep shift register. Qa-Qh are connected to IC2, and Qi-Qp are connected to IC6.
IC3 and IC7 are configured as one 16-bit deep shift register. Qa-Qh are connected to IC3, and Qi-Qp are connected to IC7.
IC4 and IC8 are configured as one 16-bit deep shift register. Qa-Qh are connected to IC4, and Qi-Qp are connected to IC8.
The control pins (!OE, LATCH, !RESET, CLK) of all shift registers are connected in parallel.
SER0 is connected to IC1.
SER1 is connected to IC2.
SER2 is connected to IC3.
SER3 is connected to IC4.
It is therefore required to update all shift registers at the same time.

Assembly instructions

LED Driver PCB

First, decide if you want to use 4 pushbutton switches (for the default firmware), 4 LEDs, or a mix (for custom firmware).

SW1 and R65 or D7 and R71

SW2 and R66 or D6 and R72

SW3 and R67 or D5 and R73

SW4 and R68 or D4 and R74

Mount all necessary SMD components. Which component should go where, can be found in the table below.

cut the header strips to the right length. Our suggestion:

cut the first strip in one 10-pin long strip, and 5 6-pin long strips.

LED chains

Building your own clock-face

If you are not buying the laser-cut clock-face that we offer, you'll be building one yourself. A consideration is that at about 20cm radius, the legs of the LEDs are long enough to form the R, G and B common lines. If you make the clock larger, you'll have to run three wires along the leds....

The "puzzle" line between the four segments stems from the fact that the laser-cutter that we have access to only goes so big. And it comes in handy for transport. The laser-cutter could handle up to 30cm outer diameter. And it could handle half a clock at once. But the 4-fold symmetry looks nice.

The laser cutter leaves a bit of brown residue near the laser-cut edges. You can sand this off with a fine sandpaper.

Connecting the LEDs

Counting clockwise, starting at the LED to the right of the topmost LED:

This is the same for each quadrant, only the connector numbers differ.

Putting it all together

Version 1.0 uses 12pin headers to connect to the LEDs, but unfortunately, 12-pin ICD connectors don't exist, so we used 14-pin ICD connectors.
Pay close attention then connecting the 14-pin connectors to the PCB! Pin 1 through 12 should line up, and pin 13 and 14 should be "floating".

Everything wired-up

As can be seen in this image, the left ICD connectors are a bit further towards the USB connector, and the right ICD connectors are a bit further to the switches. Also, the reset switch isn't mounted. We decided we would never use it, so left it out. Your version will come equipped with a reset switch

After hooking everything up, you should end up with something like this:

SV9 can be used to connect an external clock source, or a servo motor, or...

1

GND

2

VCC

3

connected to pin14 of SV10

Pin 3 has two clamping diodes attached, to limit the voltage range to GND-0.6V and VCC+0.6V.
We are considering connecting this pin through a very large valued resistor directly to the mains. In that case the clamping diodes are neccessary. The better option would be to use an optocoupler or something like that....

LEDs:

D2 is connected to VCC from SV10

D3 is connected to USB power

D4 is connected to pin17 from SV10

D5 is connected to pin18 from SV10

D6 is connected to pin15 from SV10

D7 is connected to pin16 from SV10

Switches:

Switch1 (next to R71) is connected to pin16 from SV10

Switch2 (next to R72) is connected to pin15 from SV10

Switch3 (next to R73) is connected to pin18 from SV10

Switch4 (next to R74) is connected to pin17 from SV10

Jumper settings

JP1: Power supply selection.
Open: LED driver board and microcontroller board have individual power supplies
Closed: VCC from LED driver board and microcontroller board are connected.

Programming

The software

The software supplied by BitWizard, is designed to run on the BitWizard USB-Multio board, but it should be possible to port it to other boards.
A zipfile containing the latest source code can be downloaded here: http://www.bitwizard.nl/software/rgb_clock/

Default operation

Test modes

As of software version 20120208, there are several (test) modes included.

These can be accessed in two ways:

Over USB

All modes are available.

Usage:

m [m]

For example:

m 3

jumps to the LED test mode.

Mode 0 (default)

Default operation.
PWM routine: Enabled.
Bitmap generation: Enabled.

Mode 1

Allows you to, for example, send your own RGB bitmaps to the clock with the "D", "E", and "F" commands.
PWM routine: Enabled.
Bitmap generation: Disabled.

Mode 2

Enables you to manually turn colors on and off, and also send your own bitmaps.
PWM routine: Disabled.
Bitmap generation: Disabled.

Loading custom bitmaps

Identical for each quadrant

The value should be in hex. However, it might be easyer to think binary. Each bit represents an LED.
For example, to light each even LED:

d aaaa

Or for each odd LED:

d 5555

Only one color is active in this mode. To change the active color, use the "r", "g", and "b" commands.
To turn on the red LEDs, and turn off the green and blue LEDs:

r

The same goes for the "g" and "b" commands, only the colors differ.

If you send the data quick enough (for example, with a script), it should be possible to generate some nice effects.

Complete RGB bitmap

Use the "D", "E", and "F" commands (only works in mode 1):
This is a little bit more complicated than the previous option, but gives you a lot more possibilities.
The "D" command controls the red LEDs.
The "E" command controls the green LEDs.
The "F" command controls the blue LEDs.

Each nibble represents one LED in each quadrant. Let's call the quadrants 1, 2, 4, and 8. Quadrant 1 is the bottom right, quadrant 2 top right, quadrant 4 top left, and quadrant 8 bottom left.
We only have 15 LEDs, so one of the 16 nibbles is not used:

Using the pushbuttons

Reading back the time

The "t" command outputs the current time on the clock over the serial interface:

CDC usbio/usbmultiio Wed Jan 11 18:28:22 CET 2012
> t 11:2F:03.02E0
>

The time is printed in hex, in hh:mm:ss.milliseconds

Adjusting the white-balance

Over USB

Setting the white-balance can be done with the "B" command.
Usage:

B [rValue] [gValue] [bValue]

Values are in hex. Example (this is the default setting):

B 7800 7E00 0000

This means the red LED is on from 0x0000 until 0x7800, green is on from 0x7800 until 0x7E00, and blue is on from 0x7E00 until 0x0000.
This counter counts from 0x0000 to 0xBB80.

Because the interrupt routine takes some time too, there is a minimum interval between two interrupts. This minimum was measured to be between 0x600 and 0x700. I recommend you do not set the interval between two interrupts shorter than about 0x800.

Using the pushbuttons

Not yet implemented.

Jump to bootloader

If you want to flash the controller, you need to switch to the bootloader. You can do this by pressing the pushbutton of the multio, of if you're lazy (or if the clock is hanging on a wall on the other side of the room) you can do it by issuing the "z" command.